CIRCULAR PRIME NUMBERS

CIRCULAR PRIME NUMBERS

The circular prime number are the numbers those whose circulation formations (left to right ) are also primes.

Eg : 197 is circular prime

As 197 is prime
      719 is prime ( left to right )
      971 is prime ( left to right )

      197 same

So as to solve this the 

LOGIC IS:

Make a function that checks for if the number is prime or not .

Now if the number is prime,
Circulate the number to get its new  formation.

For each formation check if t it is prime or not.
If the formation is prime,

Circulate again and make a new formation and check again

If formation isn't prime,
    terminate.

Keep on checking till you reach the same number again (  from which formations are made )

JAVA CODE

import java.util.Scanner;

public class circular_prime {

 
 static boolean isPrime(long n){
  for(long j=2;j<n;j++)
   if(n%j==0)return false;
  
  return true;
 }
 
 static int check(long n)
 { int j=1;
  while(n/10!=0)
  {
   j*=10;n/=10;
  }
  return j;
 }
 
 static boolean iscircular(long n)
 {
   int fact=check(n);
   long temp=0,temp2=n;
   while(n!=temp)
   { temp=temp2;
    temp=temp/10+(temp%10)*fact;
    temp2=temp;
    if(isPrime(temp)){}
    else return false;
   }    
     return true;
 }
 
 
 public static void main(String[] args) {
  // TODO Auto-generated method stub
  long n=0;
  
  Scanner sc=new Scanner(System.in);
  System.out.println("enter the value upto which circular primes are to be found");
  n=sc.nextLong();
  
 for(long i=2;i<=n;i++)
  if(isPrime(i))
   if(iscircular(i))
    System.out.println(i+"  :  Number is circular");

  sc.close();
 }

}